Process for the recovery of vanadium from raw titanium chloride

ABSTRACT

A PROCESS IS DISCLOSED FRO RECOVERING VANADIUM FROM SOLID TICL4-FREE RESIDUES OBTAINED IN THE PURIFICATION OF RAW TICL4 WITH H2S, WHEREIN THE SOLID RESIDUES ARE TREATED WITH OXYGEN OR AN OXYGEN-CONTAINING GS AT TEMPERATURES BETWEEN 150* AND 200*C., THEREBY OBTAINING A VOCL3CONTAINING GAS FROM WHICH THE VOCL3 IS SEPARATED IN A PRACTICALLY PURE STATE BY RECTIFICATION. THE SOLID TICL4-FREE RESIDUES ARE OBTAINED FROM THE PURIFICATION SLUDGES OF THE LIQUID RAW TICL4 BY DRYING SAME AT TEMPERATURE OF 150*180*C., IN A STREAM OF INERT GAS, PREFERABLY NITROGEN.

Dec. 7, 1971 F. FERRERO ETAL' 3,625,645

PROCESS FOR THE RECOVERY OF VANADIUM FROM RAW TITANIUM CHLORIDE Filed May 16, 1969 Shets-Sheot 1 KR M Fig. 1

INVENTORS FRANCESCO FERRERO, GIUSEPPE SIRONI, ANGELO GARBERI BY MQMMLQM ATTORNEYS Dec. 7, 1971 F, FERRERO ETAL 3,625,645

PROCESS FOR THE RECOVERY OF VANADIUM FROM RAW TITANIUM CHLORIDE Filed May 16, 1969 2 Sheets-Sheet 2 X X 10L 11L Fig. 2

INVENTORS FRANCESCO FERRERO, GIUSEPPE SlRONl ANGELO GARBERI BY m am,%w&wb

ATTORNEYS United States Patent PROCESS FOR THE RECOVERY OF VANADIUM FROM RAW TITANIUM CHLORIDE Francesco Ferrero and Giuseppe Sironi, Novara, and

Angelo Garberi, Cilavegna, Italy, assignors to Montecatini Edison S.p.A., Milan, Italy Filed May 16, 1969, Ser. No. 825,158 Claims priority, application Italy, May 20, 1968, 1 16,706A/ 68 Int. Cl. C22b 59/00; C01g 31/00 US. Cl. 23-17 8 Claims ABSTRACT OF THE DISCLOSURE The present invention relates to a process for the recovery of vanadium from raw titanium chloride. More particularly, this invention relates to a process for recovering vanadium, in the form of practically pure V001 from the residues of the purification of TiCl, from vanadium compound with hydrogen sulphide.

As is already known, the raw titanium tetrachloride obtained by chlorination of mineral rutile or other titaniferous ores (ilmenites, leucoxenes, etc.) is a yelloworange liquid containing as main impurities vanadium chlorides and oxychlorides and silicon, iron and aluminum chlorides; furthermore, it contains dissolved therein a number of gases such as C0, C0 COCl HCl, C1 Hereinafter these gases will be referred to as uncondensable gases.

Rectification allows the separation of the uncondensable gases and the silicon tetrachloride as head products. The Fe, Al, Cr. etc. impurities are eliminated as high-boiling tail products. The central fraction of the rectified product is. a clear, yellow-orange colored liquid consisting of TiCl, and vanadium compounds.

The vanadium present in the raw titanium tetrachloride in the form of soluble chloride and/ or oxychloride is only difficultly separable by rectification from the TiCl both because of its low concentration in the latter, as well as for the closeness of the respective boiling temperatures. The elimination of the vanadium is, however, indispensable for obtaining titanium tetrachloride sutficiently pure for producing TiO pigment or metal titanium.

The known processes for the separation of the vanadium from raw titanium tetrachloride consist essentially of a chemical purification of the latter by the use of various agents such as hydrogen sulphide, oleic acid, mineral oils, xanthic esters, soaps, etc.

Treatment with these substances causes the vanadium to be precipitated in the form of insoluble and non-volatile compounds, whereupon it is then possible to achieve the desired Ti-V separation by simple distillation of the TiCl,.

Among the various purifying agents, hydrogen sulphide is one of the most frequently used, both for its tested effectiveness as well as for the ease of dosing and manipulation.

The prior art purification processes with H 8 consist substantially in treating the raw TiCl, in liquid phase with a sufficient amount of gaseous H S at room tempera- "ice ture, thereby obtaining slurries relatively fluid and decantable in comparison with those obtained with the other above-mentioned agents. Although these slurries containing in suspension the solid reaction products may be distilled directly, it is nevertheless preferable to first subject them to a decanting process and then to carry out the distillation or rectification on the clarified liquid in order to avoid serious drawbacks, due to the accumulation of the solid compounds in the boiler or pot of the distillation apparatus.

The thickened sludges, since they contain a considerable amount of TiCl, (about by weight), must obviously be subjected to a process of vaporization in order to recover the titanium tetrachloride contained in them, thereby obtaining a dry TiCl -free product.

According to another process described and claimed in Serial No. 822,110, filed May 1969, this dry product containing besides the vanadium compounds also the other impurities of the raw TiCl and which is free of TiCl may be obtained directly without having to pass through the above-described wet steps, by carrying out the purification of the raw TiCL, by means of H 8 in gaseous phase at a temperature between and 180 C. By this process, in fact, the vanadium impurities separate as solid products at the same time as the solids dragged downstream of the chlorination reactor (titaniferous ore, coke, etc.) and with the volatile chlorides which desublimate or condense (FeCl FeCl ZrCl,, etc.).

This dry product, however obtained, contains prevailingly in the form of VOCl and VOCl practically all the vanadium which was present in the starting raw substance and may therefore be conveniently subjected to a process for the recovery of the vanadium itself.

Thus, the object of this invention is to provide a process for the recovery, in the form of a practically pure compound, the vanadium contained in the above-mentioned dry TiCl -free product obtained as a residue in the purification of the TiCl Another object of this invention is to recover the vanadium in the form of a valuable product such as VOCl which, considering its substantial purity, may be used directly, for instance, as a component of polymerization catalysts for olefines.

Still another object of this invention is to convert the dry solid coming from the vaporization of TiCl and containing hydrolizable products, into an inert mass which will not produce smoke when brought into contact with moisture, because it contains no more hydrolizable chlorides and, therefore, may be freely discharged into the air, thereby saving the cost of its elimination.

A still further object is to recover the vanadium by a simple and cheap system which may be directly inserted into an existing plant for the production of TiCl All these and still other objects are attained by the process of this invention, which consists in treating the solid TiCl -free residues, as obtained by the purification of the raw TiCl, which H S with oxygen or gases containing oxygen at temperatures of from to 200 C., thereby obtaining a gas containing V001 and from which the V001, may be separated in a practically pure state by rectification.

If the antecedent purification of the TiCl, with hydrogen sulphide has been carried out in the liquid phase, after the settling or filtering of the slurry one obtains a thickened sludge which is fed into a suitable vaporizer (for instance, of the screw type) where the evaporation of the TiCl, takes place in a current of a dry inert gas (for instance nitrogen, CO CO, argon, helium) at temperatures between 150 and 180 C.

The TiCl -vapors, free of vanadium but contaminated by small amounts of silicon tetrachloride, are sent either directly or after condensing, to a fractioning column from which the uncondensable gases and the silicon tetrachloride (B.P. 57.6 C.) are separated as a head product, while the tail product (B.P., 136.4 C.) constitutes the pure titanium tetrachloride which may be used directly for the desired industrial purposes.

The drying system for the thickened sludges may also include other apparatuses different from the screw-type, such as for instance heated mechanical mixers, rotary hearth furnaces, roller or rotary dryers and the like, for facilitating the separation of the gases and vapors from the solid particles and allowing the discharging of the latter.

If the solids containing the vanadium are already free of TiCl one may then proceed directly to the treatment with the oxidizing gas. 4

The dry solid product contains usually from about 5% to 20% by weight of vanadium, calculated as metallic vanadium.

The treatment of this dry solid at 150200 C. with oxidizing gases (oxygen, air or oxygen-enriched air in any ratio) may be carried out in the same apparatus as is used for the recovery of the TiCL; from the sludges, thus involving a discontinuous or intermittent process. Alternatively one may use apparatuses of the same type (that is, the above-mentioned screw-type mixers, rotary furnaces, etc.) or apparatuses of different type (for instance, of the fluid-bed type). Preferred are apparatuses provided with means for indirect heating. When not using the same apparatus as is used for the recovery of the TiCl, from the sludges, it is feasible to carry out the process in a continuous manner.

The amount of oxidizing gas used in the oxidation treatment amounts to 1 to 2 kilos of oxygen for each kg. of vanadium to be recovered. The gases produced during the oxidation consist of VOCl TiCl (formed by oxidation of the TiCl present in the solid before the oxidation), and S (formed by oxidation of the sulphur introduced as H These gases contain (respectively) 2.5-1.5 kg. of VOCl per cubic meter of gaseous mixture when using oxygen, and 1.3-0.5 kg. of VOCl when using air.

The contact time of the oxidizing gas in the apparatus for the oxidation of the solids must be sufficiently long to ensure the most complete as possible transformation of the vanadium compounds into VOCl this time depends on the partial pressure of the oxygen, on the temperature, on the kind of equipment employed, and on the contact surface between the solid and the gas.

The vapors produced during the oxidation reaction may be fractionated directly or they may be condensed at temperatures between 0 C. and 30 C., thereby obtaining a dark red liquid essentially consisting of VOCl and a little TiCl This product, rectified in a column of to 30 plates, yields a head fraction boiling between 125 and 127 C. which is a red-orange colored product consisting essentially of pure VOCl and a tail product which boils above 127 C. and which consists of VOCl and TiCl This latter fraction is preferably recycled back into the system involving the step of purification with H 8.

The following examples (and corresponding figures) are given in order to still better illustrate the inventive idea of this invention:

EXAMPLE 1 With reference to the plant schematically represented in the accompanying FIG. 1, 100 kg. of liquid raw TiCl (containing 0.17% by weight of vanadium expressed as metallic vanadium), after having been treated while stirring and at room temperature with 0.2 kg. of H S in minutes, give place to a slurry which, de-gassed with a current of dry nitrogen (600 liters) in minutes while stirring, is then discharged via line 1 into settling tank F, where it is left to settle for 2 hours.

In this way there were obtained 93.2 kg. of clarified TiCl (which goes to a rectification step via line 2) and 6.80 kg. of thickened material (containing 85% by weight of TiCh) which is conveyed through line 3 into the screw evaporator A. Here, with the screw at rest, the thickened material is dried for 4 hours at 160 C. with a stream of dry nitrogen liters/hr.) entering from line 4. The TiCl -vapors (5.8 kg.) leave through line 7, are condensed in B and ,by means of line 8, are re-united with the clarified TiCl leaving F on its way to rectification via line 2.

In evaporator A remain 0.99 kg. of a solid showing the following composition in percent by weight:

V=17.2%; Ti=13.8%; Cl=46.0%; elementary S: 10.3%; combined S=3.2%; Fe+Al 1%.

An oxygen stream (60 liters/hr.) is passed through the solid product remaining in A for a period of 3 hours. The oxygen flows in through line 5 at 170-200 C., While the screw is at rest. The vapors leaving A are thereupon conveyed directly through 9 into rectification column C, which has 16 plates and from which, by operating with a reflux of 10:1, there are obtained (through 11-D- 12) 0.18 kg. of gaseous S0 via line 14, and 0.47 kg. of head products via outlet 13 (B.P. 125127 C.; strength in VOCl 98%; the residue being substantially TiCl and 0.21 kg. of tail product from the rectification column via line 10 (B.P. 127-130 C.; having of TiCl and 30% of VOCl The tail product from line 10 is recycled back into the H 8 treatment system.

The exhausted solid (0.20 kg.) is freely discharged into the air from A through 6, by putting the screw into motion. This solid contains predominantly T iO and titanium oxychlorides. The vanadium recovered with this dry solid amounts to 0.016 kg. from which one calculates a recovery of 90.6%.

EXAMPLE 2 With reference to the plant schematically illustrated in the accompanying FIG. 2, kg./hr. of slurry (0.17% by Weight of vanadium) coming from the treatment of TiCl with H S are continuously fed through 1 into the DORR decanter or classifier A. From A 93 kg./hr. of clarified TiCl are withdrawn via line 2. This is then rectified. 7 kg./hr. of thickened slurries are discharged continuously via line 3 into the screw-evaporator B, heated at 170 C., where they are heated with 200 liters/ hr. of dry nitrogen introduced via line 4.

6.0 kg./ hr. of TiCh-vapors are removed from B via line 5 and then condensed in D, the condensate being added to the clarified product leaving the system via line 2. The nitrogen flowing out of condenser D is then re-cycled by means of the recycling pump E. Both screws, B and C, are kept in motion by carrying out the two treatments continuously. From screw B 0.99 kg./hr. of dry solids are discharged via line 6 into screw mixer C kept at a temperature of 160 C., the dry solids meeting in their path of flow a counter-current stream of air (800 liters/hr.) fed in via line 8.

The vapors coming from line 7 are fractioned in F (a column with 16 plates, operating with a reflux of 10:1) thereby obtaining (respectively) through 10 and condenser G, 0.18 kg./hr. of gaseous S0 in 13, and 0.43 kg./hr. of head products in 11) B.P. -127 C.; contents in NOCl 98%, the residue consisting substantially of TiCl From the bottom of the column F, there are discharged 0.24 kg./hr. of tail product (32% of VOCl +68% TiCh) via outlet 10. This is recycled back into the H 8 purification system.

0.22 kg./hr. of exhausted solid material containing essentially TiO titanium oxychlorides and a little vanadium are discharged from C via outlet 9. The vanadium removed with the dry solid amounts to 0.022 kg./hr. Thus, the recovery of the vanadium equals 87%.

What is claimed is:

1. A process for recovernig vanadium from solid TiCl -free residues obtained in the purification of raw TiCl with H 8, wherein said solid residues are treated with oxygen or an oxygen-containing gas in an. amount. from 1 to 2 kg. of oxygen for each kg. of vanadium present in said solid residues,

at temperatures between 150 and 200 C., thereby obtaining a VOCl -containing gas, and

thereafter separating from said gas the VOCl in a practically pure state by rectification.

2. A process according to claim 1, wherein the solid TiCl -free residues are obtained from the purification sludges of liquid raw TiCl by drying same at temperatures from 150 to 180 C. in a stream of an inert gas.

3. A process according to claim 2, wherein the inert gas is nitrogen.

4. A process according to claim 1, wherein air is used as the oxidizing gas.

5. A process according to claim 1, wherein the raw VOCl is rectified in order to yield a purified V001 with a content of more than 98% in the head and a mixture of VOCl and TiCl in the tail.

6. A process according to claim 5, wherein the tail product comprising said mixture of VOCl and TiCL; is recycled to the H28 purification stage.

7. A process according to claim 1, wherein the treatment with said oxygen or oxygen-containing gas is eifected UNITED STATES PATENTS 2,230,538 2/1941 Jenness et al. 23-87 TP 2,289,328 7/1942 Pechukas 2387 TP 2,754,255 7/1956 Stambaugh 23-87 TP 2,836,547 5/1958 Stoddard et a1 2387 TP 2,958,574 11/1960 Hansley et al. 23-87 TP 3,389,957 6/1968 Olds et al. 23-16 OTHER REFERENCES Derwent Belgian Patents Report, vol. 74 B, April 28, 1961, page A29.

20 HERBERT T. CARTER, Primary Examiner U.-S. C1. X.R.

2321, 85, 87 TP,19 V 

